1. Field of this Invention
This invention relates to polymer compositions and to blends thereof with polyethylene.
2. Prior Art
While elastic behavior in some crystalline polyolefins is known (see Quyna, R. G., Preprints of the Tidewater A.I. Ch. E. Meeting -- Williamsburg, Va., May, 1970, Celanese), polyethylene in an elastic state is not known.
Plastic packaging films, such as unmodified polyethylene, polypropylene, and polystyrene, are difficultly degradable (see Plastic Focus, vol. 4, no. 22, 7/31/72).
Attention is drawn to U.S. Pat. No. 3,299,171, Hungarian Patent No. 154,798, and M. Akiyama, S. Kawakubo and M. Kondo, Rev. Elec. Commun. Lab., (Tokyo), 12 693 (1964), Graft Copolymerization Acenaphthylene On Polyethylene.
Crystalline polymers like polyethylene may be represented as two phase systems where perfect crystals are interconnected by rubbery amorphous phases. Early modles involved "fringed micelle" structures in which most amorphous chains passed from one crystal to another. Observation of polymer single crystals demonstrated the existence of lamellae composed of regular folded chains and that such structures persist in the solid polymer where crystals are imperfect and contain defects such as chain ends, kinks and folds. The amorphous phase is far from rubberlike and involves chain ends, regular and irregular folds and tie chains (between crystallites) of various lengths. For highly crystalline polymers, the crystallites participate in superstructures and consequently stress distribution and mechanical properties depend upon the arrangement of crystals, their size and number, i.e., the polymer morphology.
It was thought that the principal effect of comonomer in polyethylene systems, beyond polar effects on adhesion, compatibility, etc., was reduction of crystallinity with concomitant reduction in stiffness modules and melting point. Principal emphasis was on effectiveness of disrupting crystallinity, dependence on geometric factors such as side chain van der Waals radius and the number of chain atoms on each side of a branch point prevented from crystallizing by the bulk and geometry of the side chain. More recently, evidence has emerged concerning the incorporation of comonomer units within crystalline regions along with crystalline defects which may be produced by a comonomer side chain, chain ends imperfections in the folded chain crystal structure of polyethylene. Comonomer effects then are case in a more complex role.